IT Questions and Answers :)

Tuesday, February 20, 2018

What is the minimum size of the IPv6 packet header?

What is the minimum size of the IPv6 packet header?

  • 36 octets
  • 32 octets
  • 40 octets
  • 48 octets 

 
What is the minimum size of the IPv6 packet header?

EXPLANATION

The IPv6 packet header has a minimum size of 40 octets. Options are implemented as extensions. This provides the opportunity to extend the protocol in the future without affecting the core packet structure.
RFC 2460; Internet Protocol, Version 6 (IPv6) Specification, S. Deering, R. Hinden (December 1998)
https://en.wikipedia.org/wiki/IPv6
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Monday, February 19, 2018

In MacOS, what terminal command will temporarily reduce the frequency of the "spinning beach ball" icon caused by a RAM shortage?

In MacOS, what terminal command will temporarily reduce the frequency of the "spinning beach ball" icon caused by a RAM shortage?

  • purge ram
  • purge mem
  • sudo purge
  • sudo clearmem 

 
In MacOS, what terminal command will temporarily reduce the frequency of the "spinning beach ball" icon caused by a RAM shortage?

EXPLANATION

Purging the memory clears on inactive memory allocation, thus making it usable to applications. Sudo purge accomplishes this.

SOURCE

http://osxdaily.com/2012/04/24/free-up-inactive-memory-in-mac-os-x-with-purge-command/
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Friday, February 16, 2018

Which of the following is NOT a PowerShell comparison operator type?

Which of the following is NOT a PowerShell comparison operator type?

  • Matching
  • Containment
  • Replacement
  • Assignment
 
 
Which of the following is NOT a PowerShell comparison operator type?

EXPLANATION

Comparison operators are used in PowerShell to compare values. There are four types of operators: equality, matching, containment, and replacement. The one big gotcha in PowerShell has to do with syntax: rather than using traditional comparison operators like < or > PowerShell uses -lt or -gt to perform comparisons.

SOURCE

https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_comparison_operators?view=powershell-5.1
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Thursday, February 15, 2018

Two organizations are partnering and sharing systems. Which of the following would outline how the shared systems interface?

Two organizations are partnering and sharing systems. Which of the following would outline how the shared systems interface?

  • BPA
  • SLA
  • ISA
  • ROA 

 
Two organizations are partnering and sharing systems. Which of the following would outline how the shared systems interface?

EXPLANATION

An interconnection security agreement (ISA) documents the technical requirements of a connection between organizations, such as the basic components, methods and levels of interconnectivity, and potential security risks.
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Wednesday, February 14, 2018

You need to encrypt and compress your backups before replicating them off site. Which is best practice, compress then encrypt, or encrypt then compress?

You need to encrypt and compress your backups before replicating them off site. Which is best practice, compress then encrypt, or encrypt then compress?

  • Neither!
  • Encrypt first!
  • Doesn't matter!
  • Compress first! 
 
You need to encrypt and compress your backups before replicating them off site. Which is best practice, compress then encrypt, or encrypt then compress?

EXPLANATION

If you encrypt the data first, it will be randomized and unintelligible by your compression application which need to compress the data in a logical format.  
Compressing then encrypting is the way to go.

SOURCE

https://stackoverflow.com/questions/4676095/when-compressing-and-encrypting-should-i-compress-first-or-encrypt-first 
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Tuesday, February 13, 2018

For every unique constraint on a column, SQL server will create which of the following?

For every unique constraint on a column, SQL server will create which of the following?

  • An entry for that column
  • A non-clustered index for that column
  • A clustered index for that column
  • A filtered index 

 
For every unique constraint on a column, SQL server will create which of the following?

EXPLANATION

For every unique constraint on a column, SQL server creates a non-clustered index. A non-clustered index has a structure separate from the data rows. It contains non-clustered index key values and each key value entry has a pointer to the data row that contains the key value.

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Unix time is the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC) on what date?

Unix time is the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC) on what date?

  • Saturday, January 1, 2000
  • Sunday, December 28, 1969
  • Thursday, January 1, 1970
  • Monday, January 1, 1900 

 
Unix time is the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC) on what date?

EXPLANATION

Unix time counts the number of seconds that have elapsed since 00:00:00 UTC on January 1, 1970. It is used in Unix-like operating systems and file formats. Because it doesn't deal with leap seconds, it is not a true representation of UTC. Check out Unix time for yourself by typing "date +%s" on the command line.

Fun fact: December 28, 1969, is Linus Torvalds' birthday, which makes him older than Unix.

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